America's senior military officer says it will take patience to win the war in Iraq, and the toughest fighting lies ahead. General Richard Myers was interviewed on British television Sunday.

General Myers, the chairman of the U.S. military joint chiefs of staff, said the war has gone well in its first 10 days, but he cautioned that a lot fighting remains to be done. "I've always said that the toughest part is yet to come. That it will not be linear in term of how tough the fight is," he said. "So, I would think the toughest fighting is ahead of us."

General Myers said the outcome of the war is not in doubt, but he urged the public to be patient, because the battle plan calls for spilling as little blood as possible. "We're going to be able to take the time we need to set the conditions, so that we do a couple of things: We spare Iraqi civilians from harm and, of course, that has been one of our principles right along; and second, so we don't put our blood and treasure, our men and women, in harm's way in an unnecessary way," he said.

General Myers also commented on the need to change tactics following Saturday's suicide car bombing that killed four American soldiers near the Iraqi city of Najaf. "I think we can adjust our tactics and our techniques and the procedures that we use to overcome that threat," he said. "It's just a reminder that there are some very desperate people out there, and we've got to be on [alert]."

In another development, the former British foreign secretary, Robin Cook, told the Sunday Mirror newspaper that British troops should be pulled out of Iraq immediately. He called the war "brutal and unnecessary," and he warned against besieging Baghdad. Mr. Cook resigned as leader of parliament two weeks ago, just before the war started.

Prime Minister Tony Blair's office, responding to Mr. Cook's comments, said the war will continue until Iraq is disarmed of weapons of mass destruction and Iraqi President Saddam Hussein is toppled.